We usually say that the allotment process ended with the Indian Reorganization Act of 1934. But that applied to the surveying of reservations into allotments. Apparently, a person could still apply through the Bureau of Land Management for an allotment in the public domain for some time after that. The General Land Office took care of issuing allotments on the Public Domain to Indians who were not living on a reservation.
According to CFR 43, Section 2530 on Indian Allottments, a person was supposed to make an application through the GLO for an allotment, and then get a certificate from the Indian Office that he or she was indeed an Indian entitled to an allotment. That certificate was supposed to be attached to the allotment application. And, here’s the clinker, “Each certificate must bear a serial number, record thereof to be kept in the Indian Office.” Obviously, that would amount to a serial number being given to each applicant. However, I have not been able to find any. We do have thousands of Indian Allottment applications filed under various Land Offices in the GLO records, and I couldn’t examine them all. But of the ones I did look at, there was no certificate with a serial number from the Indian Office. But that doesn’t mean there are none!
If you have an ancestor who received an allotment on the public domain, you can look him/her up on the BLM site: www.glorecords.blm.gov The allottment files listed under various land offices are much more similar to the regular land entry case files. They contain the application, and any correspondence about it. You can get the information and send for a copy of the file, or come in and request it.